This invention relates to spinning units in an open end spinning machine, and more particularly to the prevention of the spinning rotor in each spinning unit from being clogged by fibers fed thereinto.
Generally, in an open end spinning machine such as, for example, described in U.S. Pat. No. 3,354,626, each spinning unit includes means for feeding individually opened fibers into a spinning rotor, in which superatmospheric pressure is produced by rotation thereof. The opened fibers are formed into a yarn in the spinning rotor. The yarn is transported from the spinning rotor by a winding means. Also, in the above open end spinning machine, each of the fiber feeding means, yarn take-up means and yarn winding means is mounted on a separate driving shaft and a single motor drives these separate driving shafts through a rotation transmission mechanism including trains of gears. This motor also drives an endless belt, which is in frictional contact with spindles of the spinning rotors to rotate the same.
When the spinning machine is stopped, the fiber feeding means is first stopped to discontinue the supply of fibers to the spinning rotor, the take-up roller and winding roller are then stopped at a time when the yarn end resulting from breakage of the yarn still remains in the yarn take-up tube, which undergoes the suction effect of the subatmospheric pressure in the spinning rotor, so as to facilitate the simultaneous connection of the yarn endings in all of the spinning rotors on subsequent starting of the spinning machine. Finally, all the spinning rotors are stopped. On starting, all the spinning rotors start to rotate simultaneously, the yarn take-up rollers and winding rollers are then rotated in a reverse direction to push the yarn ends from the take-up tubes into the spinning rotors, while the fiber feeding means are operated to supply opened fibers into the spinning rotors thereby to allow them to be twisted into the reversed yarn ends. Thereafter, the take-up rollers and winding rollers are rotated in a normal, yarn winding direction.
In order to detect a possible yarn breakage during the normal spinning operation, each spinning unit is provided with a yarn breakage sensing device of the contact type allowing a yarn sensing lever thereof to be in contact the yarn to detect the breakage and to be maintained in this yarn sensing or detecting position by the yarn tension during the normal spinning operation. Typically, such a yarn breakage sensing device is illustrated in British Pat. No. 1,158,623.
With the yarn breakage sensing device of the type described above, the yarn sensing lever may not be maintained in the yarn detecting position, i.e., moved into a yarn breakage position, under the transient condition either from or to the normal spinning operation during which the spinning machine is stopping or starting by pushing down a stop push-button or a start push-button, since the yarn tension during such a transient condition is lower than that during the normal spinning operation. In order to eliminate this disadvantage of the above-described yarn breakage sensing device, heretofore, the yarn sensing lever has been designed to be forcibly moved into an inoperative position, in which it is not in contact with the yarn, by using for example an electromagnet during the transient conditions. However, since such a forced movement of the yarn detecting lever has been effected simultaneously in all of the spinning units, fibers would be supplied into not only spinning rotors in which the yarn end connecting operation has been favourably carried out, but also a spinning rotor in which the yarn end connecting operation has failed.
In the past, the number of rotations of spinning rotors was relatively low i.e. on the order of about 30,000 r.p.m., and therefore the fiber supply rate was low. Also, the spinning rotor had a relatively large inner diameter so as to apply a sufficient centrifugal force on the fibers in the low speed spinning rotor. However, recently, the rotation speed of spinning rotors has been increased to values of about two to three times 30,000 r.p.m. and accordingly the inner diameter of the spinning rotor has been decreased (this results in a decreased volume of the spinning rotor) to restrict the centrifugal force within favourable limits. Moreover, the fibers have had to be supplied at an increased rate to spin the same amount of yarn. These recent spinning conditions cause the fibers to overflow if they are supplied into a spinning rotor in which the yarn end connecting operation failed, and the spinning rotor to be clogged by the supplied fibers. Thus, there is the danger of disadvantages such as a fire occurring in the clogged spinning rotor due to frictional heat.
It is therefore a principal object of this invention to provide an open end spinning machine, in which a yarn breakage can be detected even during the transient conditions of the spinning machine and the supply of fibers into a spinning rotor can be stopped if a yarn end connecting operation has failed in the associated spinning rotor during the transient conditions.